Generally, one carrier is mainly taken into consideration in a wireless communication system although an uplink and a downlink are set to differ from each other in bandwidth. For instance, based on a single carrier, it may be able to provide a wireless communication system, in which the number of carrier configuring each of uplink and downlink is set to 1 and in which bandwidths of the uplink and downlink are symmetric to each other in general.
According to ITU (international telecommunication union), a technology candidate for IMT-Advanced is requested to support a bandwidth extended more than that of a conventional wireless communication system. Yet, frequency allocation of wider bandwidth is not globally available for many areas except some particular areas. As a technology for using fragmented small bands efficiently, there is an ongoing development of carrier aggregation (e.g., bandwidth aggregation, spectrum aggregation, etc.) to bring the same effect of using a band of logically wider bandwidth by physically bundling a plurality of bands together.
Carrier aggregation is introduced to support an increasing throughput, prevent a cost increase due to an introduction of a broadband RF device, and secure compatibility with a legacy system. Carrier aggregation is the technology for enabling data to be exchanged between a user equipment and a base station through a plurality of bundles of carriers by bandwidth unit defined in a legacy wireless communication (e.g., LTE system in case of LTE-A system, IEEE 802.16e system in case of IEEE 802.16m system). In this case, a carrier of a bandwidth unit defined in a legacy wireless communication system may be called a component carrier (hereinafter abbreviated CC). For instance, the carrier aggregation technology may include a scheme of supporting a system bandwidth up to maximum 100 MHz by making a bundle of maximum 5 CCs despite that one CC supports a bandwidth of 5 MHz, 10 MHz or 20 MHz.
Meanwhile, a user equipment may receive a paging message containing information, which indicates system information modification) by monitoring a downlink channel. However, in case that multi-carriers are applied according to the carrier aggregation technology, a method for a user equipment to receive information on system information modification has not been discussed in detail.